Various types of tests related to patient diagnosis and therapy can be performed by analysis of a sample of a patient's infection, bodily fluid or abscess for an analyte of interest. Patient samples are typically placed in sample vials, the vials transported to a clinical laboratory, placed into racks on an automated clinical analyzer and sample is extracted from the vials. Subsequently, samples are combined in reaction vessels with various reagents extracted from reagent cartridges; the mixture is possibly incubated before being analyzed to aid in treatment of the patient. Interrogating measurements, turbidimetric or fluorometric or the like, are made to ascertain end-point or reaction rate values from which the amount of analyte in the sample may be determined, using well-known calibration techniques.
Automated clinical analyzers improve operating efficiency by providing results more rapidly while minimizing operator or technician error. Due to increasing demands on clinical laboratories regarding assay throughput, the efficiency of handling patient samples and reagents within an analyzer continually needs to be increased, and an important factor is the ability to quickly position a plurality of different samples or reagents at an appropriate liquid extraction location.
The sample rack is usually placed by an operator in an input portion of the analyzer and automatically moved by the analyzer to an aliquotting location where an aliquot of the liquid patient sample is extracted, usually by aspiration using a hollow probe from the sample container. Aliquot samples from a number of different patient samples may be dispensed into a plurality of interim vessels or wells formed as an integral array of small open cup-like vessels, herein called an aliquot vessel array, like that described in U.S. patent Ser. No. 10/037,512, assigned to the assignee of the present invention. Aliquot vessel arrays are transported to a sampling location where an appropriate amount of the aliquot sample is extracted by a sampling probe and dispensed by a sampling probe into a reaction cuvette. In addition, reagent(s) required to conduct specified assays are extracted at a reagenting location from appropriate reagent cartridge(s) using hollow probes that are subsequently shuttled to a reagent dispensing location where reagent(s) are dispensed into the reaction cuvette.
In order to maintain high assay throughput, it is advantageous that sampling probes be quickly shuttled between sampling locations and reaction cuvettes and that reagenting probes be quickly shuttled between reagenting locations and reaction cuvettes. It is also advantageous that reagent cartridges be quickly shuttled between on-board storage locations and reagenting locations. In all of these shuttling and positioning operations, it is desirable that the aliquot vessel arrays, reagent cartridges, sampling probes, and reagenting probes be accurately and repeatably positioned at their selected locations. Motorized drivebelts are frequently employed in shuttling operations like described, however the drivebelts are known to stretch from their original dimensions in long term repeated use making it difficult to repeatably position a probe or cartridge or the like at its intended location. Furthermore, when the direction of travel of a drivebelt is rapidly reversed, the drivebelt may dislodge from an associated pulley and belt or sprocket and chain unless it is maintained at a tension of sufficient strength.